Method and system for scene change detection

ABSTRACT

A method, in one exemplary embodiment, for automatically detecting scene changes within a digital video sequence including a succession of frames, including computing metrics, for each of a plurality of frames from a digital video sequence, the metric of a frame being a measure of distance between the frame and a given frame, identifying a candidate frame for which the metric of the candidate frame differs from the metric of the predecessor frame to the candidate frame, by at least a first threshold, determining whether the metrics of successive ones of each of a first plurality of frames, successively following the candidate frame, differ from one another by less than a second threshold, and further determining whether the metrics of each frame of a second plurality of frames, successively preceding the candidate frame, are larger than a third threshold. A system, of one exemplary embodiment, is also described and claimed.

FIELD OF THE INVENTION

The present invention relates to video processing, and more specificallyto automatic scene change detection for digital video sequences offrames.

A portion of the disclosure of this patent document contains materialwhich is subject to copyright protection. The copyright owner has noobjection to the facsimile reproduction by anyone of the patent documentor the patent disclosure, as it appears in the Patent and TrademarkOffice patent file or records, but otherwise reserves all copyrightrights whatsoever.

BACKGROUND OF THE INVENTION

Scene change detection (also referred to in the literature as “shotchange detection”) is the process of identifying changes in the scenecontent of a video sequence. Scene change detection is primarily used tosegment video into scenes, and facilitate browsing of video sequencesand retrieval of desired video content.

Scene changes can occur as abrupt changes when a frame from one shot isfollowed by a frame from a different shot, and as gradual transitionssuch as fade-ins and fade-outs.

A survey of scene change algorithms is provided in Gargi, U., Kasturi,R. and Strayer, Susan, “Performance Characterization ofVideo-Shot-Change Detection Methods,” IEEE Transactions on Circuits andSystems for Video Technology, Vol. 10, No. 1, February 2000, pages 1-13.One class of algorithms used to perform automatic scene detection iscolor histogram methods. The difference between color histograms ofconsecutive frames is determined, and large frame differences areflagged as possible scene changes. Another class of algorithms performsscene detection directly on MPEG compressed video, using discrete cosinetransform (DCT) and motion prediction information.

A reference for various metrics used for scene change detection, isFord, R. M., Robson, C., Temple, D. and Gerlach, M., “Metrics for SceneChange Detection in Digital Video Sequences,” in Proceedings of IEEEInternational Conference on Multimedia Computing and Systems, Jul. 3-6,1997, Ottawa, Ontario, Canada.

U.S. Pat. No. 5,956,026 of Ratakonda describes a scene change detectionalgorithm of Lagendijk that selects scene change locations based onminimization of an action integral.

U.S. Pat. No. 6,014,183 of Hoang describes a method and system forretrieving frames of video data from a display control device andautomatically detecting scene changes. Hoang detects scene changes bycomparing pixel color values in successive frames.

Microsoft MovieMaker™ and Pinnacle Studio DV™ include scene changedetection features.

Prior art scene change detection algorithms suffer from a shortcoming inthat intermittent effects within a video shot, such as lighting changes,camera flashes, or a bird flying in and out of a scene, can producesignificant changes in color histograms and be interpreted falsely asscene changes. Hoang (col. (col. 8, lines 1-16, and FIG. 8) describesexamining a predetermined number of frames in order to determine whethera potential scene change should be considered a bona fide scene change.This serves to filter out isolated events such as flashbulbs going off.Hoang compares frames following a potential scene change with an initialframe, immediately prior to the scene change.

Hoang's method works well to filter out abrupt scene changes, such asthe change indicated in FIG. 8 of Hoang. However, Hoang's method canfail to detect bona fide scene changes that are gradual. For gradualscene changes, the differences between frames may not be large enough toexceed Hoang's threshold, and, as a result, Hoang may overlook thegradual scene changes.

SUMMARY OF THE INVENTION

The present invention provides a method and system for automaticallydetecting scene changes in a digital video sequence. The presentinvention can be used to reduce false detections due to intermittenteffects within the video sequence, by considering successive framedifferences within a window of frames. In a preferred embodiment of thepresent invention, a frame history of a number, n, of frames is analyzedfor existence of scene changes. In a preferred embodiment of the presentinvention, starting from the last frame in the frame history, denoted asthe given frame, a search is made running backwards in time from thegiven frame for the presence of a candidate scene change, indicated by adifference between two successive frames. When such a candidate scenechange is encountered, a determination is made as to whether (i)successive frames following the scene change are similar to one another,and (ii) successive frames preceding the scene change are significantlydifferent from the given frame.

This filters out brief intermittent effects. For example, if a cameraflashes at frame j and the flash effect lasts-briefly for x frames, thenthe present invention does not flag frame j nor frame j+x as a scenechange. Frame j is not flagged, since frame j+x is not similar to framej+x+1, and thus condition (i) fails. Frame j+x is not flagged, sinceframe j−1 and the given frame are not significantly different, and thuscondition (ii) fails.

There is thus provided in accordance with a preferred embodiment of thepresent invention a method for automatically detecting scene changeswithin a digital video sequence including a succession of frames,including computing metrics for each of a plurality of frames from adigital video sequence, the metric of a frame being a measure ofdistance between the frame and a given frame, identifying a candidateframe for which the metric of the candidate frame differs from themetric of the predecessor frame to the candidate frame, by at least afirst threshold, determining whether the metrics of successive ones ofeach of a first plurality of frames, successively following thecandidate frame, differ from one another by less than a secondthreshold, and further determining whether the metrics of each frame ofa second plurality of frames, successively preceding the candidateframe, are larger than a third threshold.

There is further provided in accordance with a preferred embodiment ofthe present invention a system for automatically detecting scene changeswithin a digital video sequence including a succession of frames,including a processor computing metrics for each of a plurality offrames from a digital video sequence, the metric of a frame being ameasure of distance between the frame and a given frame (which also maybe referred to as a current frame), a frame identifier identifying acandidate frame for which the metric of the candidate frame differs fromthe metric of the predecessor frame to the candidate frame, by at leasta first threshold, and a comparator determining whether the metrics ofsuccessive ones of each of a first plurality of frames, successivelyfollowing the candidate frame, differ from one another by less than asecond threshold, and determining whether the metrics of each frame of asecond plurality of frames, successively preceding the candidate frame,are larger than a third threshold.

There is yet further provided in accordance with a preferred embodimentof the present invention a method for automatically detecting scenechanges within a digital video sequence including a succession offrames, including computing metrics for each of a plurality of framesfrom a digital video sequence, the metric of a frame being a measure ofdistance between the frame and an initial frame, identifying a candidateframe for which the metric of the candidate frame differs from themetric of the predecessor frame to the candidate frame, by at least afirst threshold, determining whether the metrics of successive ones ofeach of a first plurality of frames, successively preceding thecandidate frame, differ from one another by less than a secondthreshold, further determining whether the metrics of each frame of asecond plurality of frames, successively following the candidate frame,are larger than a third threshold.

There is additionally provided in accordance with a preferred embodimentof the present invention a system for automatically detecting scenechanges within a digital video sequence including a succession offrames, including a processor computing metrics for each of a pluralityof frames from a digital video sequence, the metric of a frame being ameasure of distance between the frame and an initial frame, a frameidentifier identifying a candidate frame for which the metric of thecandidate frame differs from the metric of the predecessor frame to thecandidate frame, by at least a first threshold, and a comparatordetermining whether the metrics of successive ones of each of a firstplurality of frames, successively preceding the candidate frame, differfrom one another by less than a second threshold, and determiningwhether the metrics of each frame of a second plurality of frames,successively following the candidate frame, are larger than a thirdthreshold.

There is moreover provided in accordance with a preferred embodiment ofthe present invention a method for automatically detecting scene changeswithin a digital video sequence including a succession of frames,including identifying a candidate frame that differs substantially fromthe predecessor frame to the candidate frame, determining whether afirst plurality of frames, successively following the candidate frame,are substantially similar to one another, and further determiningwhether each of a second plurality of frames, successively preceding thecandidate frame, differ substantially from a current frame, wherein thecurrent frame follows the first plurality of frames.

There is further provided in accordance with a preferred embodiment ofthe present invention a system for automatically detecting scene changeswithin a digital video sequence including a succession of frames,including a frame identifier identifying a candidate frame that differssubstantially from the predecessor frame to the candidate frame, and acomparator determining whether a first plurality of frames, successivelyfollowing the candidate frame, are substantially similar to one another,and determining whether each of a second plurality of frames,successively preceding the candidate frame, differs substantially from acurrent frame, wherein the current frame follows the first plurality offrames.

There is yet further provided in accordance with a preferred embodimentof the present invention a method for automatically detecting scenechanges within a digital video sequence including a succession offrames, including identifying a candidate frame that differssubstantially from the predecessor frame to the candidate frame,determining whether a first plurality of frames, successively precedingthe candidate frame, are substantially similar to one another, andfurther determining whether each of a second plurality of frames,successively following the candidate frame, differs substantially froman initial frame, wherein the initial frame precedes the first pluralityof frames.

There is additionally provided in accordance with a preferred embodimentof the present invention a system for automatically detecting scenechanges within a digital video sequence including a succession offrames, including a frame identifier identifying a candidate frame thatdiffers substantially from the predecessor frame to the candidate frame,and a comparator determining whether a first plurality of frames,successively preceding the candidate frame, are substantially similar toone another, and determining whether each of a second plurality offrames, successively following the candidate frame, differssubstantially from an initial frame, wherein the initial frame precedesthe first plurality of frames.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be more fully understood and appreciated fromthe following detailed description, taken in conjunction with thedrawings in which:

FIG. 1 is a simplified illustration of a scene detector segmenting avideo sequence into scenes and displaying representative frames forscenes;

FIG. 2 is a prior art illustration of a method for filtering outcandidates for scene changes when the duration of a change is shorterthan a predetermined number of frames;

FIG. 3 is an illustration of a scene change detector in accordance witha preferred embodiment of the present invention;

FIG. 4 is an illustration of a false scene detection that is overcome bythe present invention;

FIG. 5 is a simplified illustration of an arrangement of frames used ina preferred embodiment of the present invention;

FIG. 6 is a simplified flowchart of a preferred embodiment of thepresent invention; and

FIGS. 7A and 7B are flowcharts for the algorithm included in thesoftware listing of Appendix A.

FIG. 8 shows an example of a data processing system according to oneexemplary embodiment of the invention.

FIG. 9 shows an example of a machine readable medium whichprovides/stores executable computer program instructions which whenexecuted by a data processing system cause the system to perform atleast one of various methods of the invention.

LIST OF APPENDICES

Appendix A is a software listing of an algorithm that automaticallyderives scene changes from within a digital video sequence.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

The present invention provides a method and system for automatic scenechange detection for a digital video sequence.

Reference is now made to FIG. 1, which is a simplified illustration of ascene detector segmenting a video sequence into scenes and displayingrepresentative frames for scenes. Shown in FIG. 1 is a digital videoclip 110 being played within window 120 and automatically beingsegmented into scenes. Digital video clip 110 includes a plurality offrames that naturally group together into scenes. Automatic scene changedetection software processes the frames of video clip 110 and determinesthe frames that are located at the beginnings and the ends of scenes.Frames 130 are representative frames for each scene, and are displayedto enable a user to readily identify the scenes of video clip 110.Preferably, the first frame of each scene is displayed. Also indicatedin FIG. 1 are the time codes 140 for each scene, so that a user canadvance within video clip 110 to a desired scene.

FIG. 1 also illustrates a user interface for an automatic scene changedetection system. Buttons 151, 153, 155, 157 and 159 control theplayback of video clip 110. Button 151 is used to play video clip 110 atnormal speed. Button 153 is used to pause the play. Button 155 is usedto jump to the beginning of video clip 110, and button 157 is used tojump to the end of video clip 110. Button 159 is used to stop the play.Progress bar 160 indicates the position of the frames being displayed inwindow 120 relative to the entire digital video clip 110. Sensitivityslider 170 is used to adjust the thresholds for scene detection. As thevalues of the threshold parameters are increased, the number of distinctscenes into which video clip 110 is segmented decreases.

Button 180 is used by a user to remove scenes that have been detected.This serves to manually refine the automatic scene detection results bypruning out spurious or unwanted scene segmentations.

Reference is now made to FIG. 2, which is a prior art illustrationsimilar to FIG. 8 of Hoang, of a method for filtering out candidates forscene changes when the duration of a change is shorter than apredetermined number of frames. Shown in FIG. 2 is a short segment 210,which is a candidate for a scene change. In order to determine whethersegment 210 is a bona fide scene change, Hoang compares each of apredetermined number of frames y with initial frame x, that is situatedimmediately before the scene change. If some of frames y are similar toframe x, such as frames 215, this indicates that the width AB of thechange is too small, and it is not marked as a scene change.

For scene change 220, however, the duration of the change is long, asevidenced by the width CD of the change, and each of frames y isdetermined to be different from frame x. As such, candidate scene change220 is flagged as a bona fide scene change.

The scene changes indicated by AB and CD are abrupt changes. Other typesof scene changes, such as the change indicated by segment EF, may bemore gradual. Typical types of gradual scene changes are video fade-insand fade-outs, where the end of a first scene gradually fades into thebeginning of a second scene. For such scene changes, the method of Hoangmay fail to detect a bona fide change. As illustrated in FIG. 2, thesegment EF may in fact be long enough to include the predeterminednumber of frames, but some of frames y may compare favorably with framex, indicating that the scene change is not an actual change—when in factit is.

Reference is now made to FIG. 3, which an illustration of a scene changedetector in accordance with a preferred embodiment of the presentinvention. When the present invention encounters a candidate 310 for ascene change, it compares frames y following the scene change with aninitial frame x that is a distance GH behind the scene change. As inFIG. 2, this serves to filter out candidate 310 as not being a bona fidescene change, and successfully identifies scene change 320 as being areal scene change. In addition, the method of the present inventionovercomes prior art limitations and successfully identifies gradualscene change 330 as a bona fide scene change, since it compares frames ywith an initial frame x that is well behind the start of the scenechange.

As will be seen in the ensuing discussion, the present inventionprocesses frames in reverse order, beginning with a current frame andproceeding backwards in time. Thus, with reference to FIG. 3, theleftmost frame is a latest frame—a current frame, and the frames to itsright are previous frames. This is indicated in the right-to-leftdirection of axis 340. FIG. 3 was drawn this way in order to compare itdirectly with prior art FIG. 2. However, in subsequent figures, the timeorder runs in the conventional left-to-right direction.

Reference is now made to FIG. 4, which is an illustration of a falsescene detection that is overcome by the present invention. Shown in FIG.4 is a slowly changing effect 400 from J to K, followed by a rapidchange from K to L. For example, a baseball could be graduallyapproaching a camera in a succession of frames from J to K, and thensuddenly disappear from the scene at frame L. The prior art approach ofHoang detects potential scene changes by comparing successive frames. Ifthe frame changes from J to K are sufficiently small, then Hoang willnot detect a scene change until the rapid change from K to L occurs.Hoang will then compare the frame at K (marked x) with the framesfollowing it (marked y), and since none of the y frames are similar tothe x frame, Hoang will mistakenly identify a scene change betweenframes K and L.

In distinction, the present invention detects potential scene changes bycomparing frames with an initial frame (marked x). Thus, with respect tothe effect 420, at some point along the grade from J to K, a frame willdiffer significantly from frame x, and the present invention will flagit as a candidate scene change. The present invention will then compareseveral frames following the candidate scene change (marked y) withinitial frame x, and conclude that there are frames following thecandidate scene change that are similar to frame x. As a result, usingthe present invention the candidate scene change will be rejected, andno false scene change will be marked.

Reference is now made to FIG. 5, which is a simplified illustration of apreferred embodiment of the present invention. Shown in FIG. 5 areframes from a video clip 500. Included are a current frame 510, frames520 and 530 that border a scene change between a first scene and asecond scene of video clip 500, frames 540 from the second scene ofvideo clip 500, and frames 550 from the first scene of video clip 500.Frame 520 marks the end of the first scene and frame 530 marks thebeginning of the second scene.

In a preferred embodiment, the present invention operates by determiningthat frames 520 and 530 are substantially different, thereby indicatingthat these frames are candidate frames for a scene change. Frames can becompared with one another by various metrics, as described hereinabove.In a preferred embodiment of the present invention, histograms are used.The individual color channels of each frame are binned into histogrambins, and the frequencies of color data in each bin are tallied. Forexample, with respect to an RGB color system, the red, green and bluevalues of each pixel typically range from 0 to 255 (8 bits). If 16uniform bins are used for each color channel, then each red value, r,0<=r<=255, belongs to bin number r>>4, and similarly for each blue andgreen value. The frequencies of red values in the 16 bins are tabulatedand summarized in a histogram hr[i], 0<=i<=15, and similarly for thegreen and blue values.

In a preferred embodiment of the present invention, pixel color valuesof a frame are sub-sampled on a sample grid, rather than sampled atevery pixel, in order to speed up the processing.

Histograms for two flames are preferably compared by summing absolutevalues of the differences in their frequencies, for each bin and foreach color channel. Specifically, for the above case of 16 bins, what issummed is: $\begin{matrix}{\,_{i = 0}^{15}\left( {{{{{hr1}\lbrack i\rbrack} - {{hr2}\lbrack i\rbrack}}} + {{{{hg1}\lbrack i\rbrack} - {{hg2}\lbrack i\rbrack}}} + {{{{hb1}\lbrack i\rbrack} - {{hb2}\lbrack i\rbrack}}}} \right)} & (1)\end{matrix}$where hr1, hg1, hb1 are red, green and blue histograms for a firstframe, and hr2, hg2 and hb2 are red, green and blue histograms for asecond flame. If the sum in Equation (1) exceeds a prescribed upperthreshold, then the frames are deemed substantially different.Similarly, if one were interested in determining if two frames aresubstantially similar, then this can be based on whether the sum inEquation (1) is less than a prescribed lower threshold.

It is apparent to those skilled in the art that other functions can beused for histogram comparison, besides the absolute value function. Forexample, Equation (1) could be replaced by a sum of squares of histogramdifferences, instead of a sum of absolute values.

In a preferred embodiment, the present invention determines if at leastm frames 540 following frame 530 are substantially similar to oneanother, and determines if at least m frames 550 preceding frame 520differ substantially from current frame 510, where m is a predeterminedlength of frames. It is apparent to those skilled in the art thatdifferent values of m may be used for the required numbers of frames 540and 550.

If it is determined that at least m frames 540 are substantially similarto one another and that at least m frames 550 differ substantially fromflame 510, then frames 520 and 530 are marked as a scene change.Referring to graph 560, which indicates the general nature of a scenechange, candidate flames 520 and 530 are marked as a scene change whenthe distances AB and CD are each at least m flames.

With respect to U.S. Pat. No. 6,014,183 of Hoang, the method of Hoangcompares each of frames 550 to frame 530, as described hereinabove withreference to FIG. 2. In distinction, the present invention comparesframes 550 to flame 510, which is at least m flames distant from thescene change.

Reference is now made to FIG. 6, which is a simplified flowchart of apreferred embodiment of the present invention. At step 610 measures ofdifference are computed between frames F[i] of a digital video and acurrent frame, F. The frame index, i, runs backwards in time, with i=0corresponding to the frame immediately preceding frame F, and with i=1corresponding to the frame preceding frame F[0]. In a preferredembodiment, the measures of difference are based on histograms.

At step 620 a frame F[j] is identified that differs substantially fromframe F[j−1], based on an upper threshold TA. Frames F[j] and F[j−1]become candidates for a scene change, similar to frames 520 and 530(FIG. 5). The comparison between frames F[j−1] and F[j] is based on thedifference d(F[j], F)−d(F[j−1], F). It would be more precise to makethis comparison by computing d(F[j], F[j−1]), but this would entailadditional processing and slow down the scene detection. By virtue ofthe mathematical “triangle inequality,” an affirmative determinationthat d(F[j],F)−d(F[j−1],F)>TA implies that in fact d(F[j], F[j−1])>TA.However, the converse is not necessarily true.

At step 630 a determination is made if each of the m consecutive framesF[j−1] and F[j−i−1], 1<=i<=m, are substantially similar, based on alower threshold TB. If the determination at step 630 is negative, thencontrol returns back to step 620. Otherwise, if the determination atstep 630 is positive, then a determination is made at step 640 if the mframes F[j+i], 1<=i<=m, are each substantially different from currentframe F, based on an upper threshold TC. If the determination at step640 is negative, then control returns back to step 620. Otherwise, ifthe determination at step 640 is positive, then frame F[j] is marked asbeing at the beginning of a scene.

In a preferred embodiment of the present invention, if a frame precedingframe F[j] is found to be substantially similar to frame F, then frameF[j] is not marked as being at the beginning of a scene.

Reference is now made to FIGS. 7A and 7B, in conjunction with the methodAnalyseFrame( ) in Appendix A. Appendix A is a software listing for analgorithm that derives scene changes from within a digital videosequence, and FIGS. 7A and 7B are simplified flowcharts of the algorithmof Appendix A. In a preferred embodiment, the present invention operatesrelative to a current frame, F, corresponding to a time t, and processesa number, SigHist, of frames prior to the current frame. The numberSigHist is a parameter for the number of frames in a frame historyconsidered to be significant for analysis of scene change. As mentionedhereinabove with reference to FIG. 6, preferably, the present inventioncomputes distances d(F[j], F) between frames F[j] and current frame F,where frames F[j] are frames prior to frame F. As with FIG. 6, in thediscussion of FIGS. 7A and 7B the notation F[j] refers to the frame thatis j frames prior to (i.e., to the left of) frame F. I.e., thesequential index j runs backwards from current frame F.

Processing begins at step 700. At step 705, key variables areinitialized. At step 710 a loop indexed on a counter j begins, with jinitialized to j=1. The counter j counts backwards from current frame F.Thus j=0 refers to the frame prior to frame F, j=1 refers to the framethat is two frames prior to frame-F, etc. A determination is madewhether firstDif equals −1. If step 710 determines that firstDif equals−1, then lastSame is set to j at step 715 and a determination is made atstep 720 whether d(F[j], F) and d(F[j−1], F) differ by an upperthreshold TA. The purpose of this test is to determine whether F[j−1]and F[j] are significantly different, and, as mentioned hereinabove, isbased on d(F[j], F)−d(F[j−1], F) instead of on d(F[j−1], F[j]), sincethe latter distance is not one of the precomputed distances. Avoidingdirect computation of the distances d(F[j−1], F[j]) serves to speed upthe frame processing.

If step 720 determines that the relevant difference exceeds thresholdTA, then at step 725 firstDif is set to j. This signifies that the firstplace prior to frame F where a significant change occurs is betweenframes F[j] and F[j−1], similar to frames 520 and 530 (FIG. 5). FramesF[j] becomes a candidate frame, F*, for a scene change. Control thenpasses to step 750, where the counter j is incremented. If step 720determines that the relevant difference is not less than TA, thencontrol passes directly to step 750.

If step 710 determines that firstDif does not equal −1, then controlpasses to step 730 where a test is made as to whether F[j] and F differby more than an upper threshold TB. Observe that firstDif will not equal−1 only if step 720 already found a candidate frame F* for a scenechange. If step 730 determines than F[j] and F do differ by more thanthreshold TB, then at step 735 nDifs is incremented. The variable nDifscounts the number of frames prior to (i.e., to the left of) frame F*which differ significantly from the current frame F. After step 735 iscomplete, control passes to step 740. If step 730 determines that F[j]and F do not differ by more than TB, then control passes directly tostep 740. Observe that frame F[j] is being compared to current frame F,and not to candidate frame F*.

At step 740 a determination is made as to whether frames F[j] and F aresubstantially similar; specifically, whether the distance between framesF[j] and frame F is less than a lower threshold TC. If such a frame F[j]is found, then the variable lastSame is set to j at step 745, indicatingthat a frame preceding (i.e., to the left of) candidate frame F* issubstantially similar to current frame F, and control passes to step750. Otherwise, control passes directly from step 740 to step 750.

At step 755 a determination is made as to whether the loop on j iscomplete. If j is less than SigHist, then the loop continues and controlpasses back to step 110. Otherwise, control passes to part B of thealgorithm (FIG. 7B), where a determination is made as to whether frameF* is to be marked as, a scene change, based on the values of firstDif,nDifs and lastSame.

At step 760 a determination is made as to whether firstDif exceedsFrameHist/3, where FrameHist is a size for a frame history buffer. Ifso, then at least FrameHist/3 frames following frame F* aresubstantially similar. At step 765 a further determination is made as towhether nDifs exceeds FrameHist/3. If so, then at least FrameHist/3frames prior to frame F* are substantially different from current frameF. At step 770 yet a further determination is made as to whetherlastSame is less than or equal to firstDif. If so, then there are noframes prior to F*, among the SigHist frames processed, which aresubstantially similar to current frame F. If any of the tests at steps760, 765 and 770 are negative, then candidate frame F* is rejected, andprocessing terminates at step 780. If the tests at steps 760, 765 and770 are all affirmative, then candidate frame F* is marked as a bonafide scene change, and processing terminates at step 780. Since frame F*denotes the frame that is firstDif+1 frames prior to the current frameF, the time code for the first frame of the new scene (i.e., the frameimmediately following frame F*) istime=t−firstDif*frameAvgTimeperFrame.  (2)This timecode is stored in an array SceneChange. This represents thetime code for the first frame in the new scene.

FIG. 8 shows an example of a digital processing system which may be usedwith the present invention. The digital processing system 800 includes aprocessor 801 and a memory 802 which are coupled together by a bus 803.The bus is also coupled to a video I/O port 804 which is in turn coupledto a camera 805. The bus 803 is also coupled to an I/O controller 806which in turn is coupled to several I/O (input/output) devices 807. Itwill be appreciated that in one embodiment, the data processing system800 may be a conventional general purpose computer having amicroprocessor, which is the processor 802, and DRAM memory which servesas the memory 802. Typically, other memory elements may be utilized in adigital processing system such as a magnetic hard disk and other typesof mass storage. The video input/output port 804 allows a camera 805 toinput into the memory 802 various frames of video which can then beprocessed according to the scene change detection methods of the presentinvention. The I/O controllers 806 allow a user of the system 800 tointeract with the system by providing commands to the system or data tothe system. Examples of input/output devices 807 include mice,keyboards, printers, scanners, display devices such as liquid crystaldisplays or CRT displays. In one exemplary embodiment, the camera 805may be a conventional video camera which is a digital camera having afirewire (IEEE 1394) port. The video I/O port 804 may be a correspondingfirewire port. Typically, the camera 805 will transmit video framesthrough the port 804 and through the bus 803 into the memory 802 wherethese frames can then be analyzed for scene change detection by usingsoftware which may practice various different embodiments of the presentinvention.

FIG. 9 shows an example of a machine readable media such as a memorydevice such as DRAM or a magnetic hard disk which stores executablecomputer program instructions which, when executed by a data processingsystem, cause this system to perform at least one of the various methodsof the present invention. This executable software and data may bestored in various places including, for example, in DRAM, which isvolatile, or in non-volatile storage devices such as magnetic harddisks. Portions of this software and/or data may be stored in any one ofthese devices. The video control/driver software 851 provides necessarycontrols and driver software for allowing for inputting and outputtingof video frames to the video I/O port 804. The memory 852 is used tostore computed metrics of the various frames which then can be processedby the comparator and frame identifier software 854. The comparator andframe identifier software compares the metrics in the manner describedin the various methods of the present invention in order to identify aframe indicating a scene change. The metric computation software 853provides the software which computes the metrics for each frameaccording to the various different embodiments of the present invention.

Reference is now made to Appendix A, which includes a software listingfor an algorithm that derives scene changes from within a digital videosequence. The method SceneList::AnalyseFrame(BYTE *pData, double time)processes a sequence of video frames, identifies individual sceneswithin the video, and records the results in an array m_SceneList thatstores the time codes for the first frame of each identified scene.AnalyseFrame( ) has two calling parameters; namely, a pointer pData intothe color pixel data of a current frame within a sequence of videoframes, and a current time that corresponds to the time code for thecurrent frame. AnalyseFrame( ) is called repeatedly as each additionalvideo frame of data is processed, and it searches for a scene change,processing a number of frames backwards from the current frame.

The lines of code t = time − firstDif*m_frameAvgTimePerFrame;if(m_nCurSceneNo < MAX_SCENES){   m_SceneList[m_nCurSceneNo] = t;at the end of AnalyseFrame( ) store timecode t at position m_nCurSceneNowithin array m_SceneList. The timecode t is calculated backwards from acurrent time, t=time, by going back a number, firstDif, of frames. Thearray m_SceneList thus stores the time codes for the start of each newscene in the video sequence.

The number firstDif is the index of the first frame prior to a currentframe, that differs from it significantly. The test for this is at theline if(diffHist[j] − diffHist[j−1] > st){   // We found a candidate:  firstDif = j;

at which firstDif is flagged when diffHist[j] and diffHist[j−1] differby more than a threshold, st. The array diffHist[j] stores thehistogram-based differences between the frame that is j+1 frames priorto the current frame, and the current frame, as indicated in FIG. 2. Asabove, the index j runs backwards in time. The calculation of diffHist[] is performed at the lines for(i=0;i<nB;i++){     totalDiff+=fabs(m_oldRBuckets[k][i] − m_RBuckets[i]);     totalDiff+=fabs(m_oldGBuckets[k][i] − m_GBuckets[i]);     totalDiff+=fabs(m_oldBBuckets[k][i] − m_BBuckets[i]);   }   diffHist[j] =totalDiff;The arrays m_oldRBuckets[ ][ ], m_oldGBuckets[ ][ ], and m_oldBBuckets[][ ] store histograms for frames prior to the current frame, and thearrays m_RBuckets[ ], m_GBuckets[ ] and m_BBuckets[ ] store histogramsfor the current frame. Thus diffHist[0], for example, represents thedifference between the current frame and the frame prior to the currentframe.

Note that the histograms m_RBuckets[ ], m_GBuckets[ ] and m_BBuckets[ ]are created by sampling the three color channels at a sampling gridspaced by units of m_grid. This is effectuated by the linesfor(r=0;r<m_imgHeight;r += m_grid){   px = pData + 3*r*m_imgHeight;  for(c=0;c<m_imgWidth;c += m_grid){     blue = px[0];     green =px[1];     red = px[2];     red >>= m_scale;     green >>= m_scale;    blue >>= m_scale;     m_RBuckets[red] += (float)wt;    m_GBuckets[green] += (float)wt;     m_BBuckets[blue] += (float)wt;    px += 3*m_grid;

The arrays m_oldRBuckets[ ][ ], m_oldGBuckets[ ][ ], and m_oldBBuckets[][ ] are circular frame buffers for each color channel, that can storeup to a maximum of m_nFrameHist frames in their histories. The lines //Frame count from the start of the effect:   int frameNum = (unsignedint) (time/m_frameAvgTimePerFrame);   // index into circular buffer ofhistorical frame statistics:   int nF = frameNum % m_nFrameHist;  for(i=0;i<nB;i++){     m_oldRBuckets[nF][i] = m_RBuckets[i];    m_oldGBuckets[nF][i] = m_GBuckets[i];     m_oldBBuckets[nF][i] =m_BBuckets[i];     m_RBuckets[i] = 0;     m_GBuckets[i] = 0;    m_BBuckets[i] = 0;   }write the latest frame histogram data into position NF, in the middle ofthe circular buffer. This position becomes the head for the storedframes, with the data for the m_nFrameHist frames prior to frame NFstored behind it in a circular wrap-around fashion.

Similarly, the lines for(j=0;j < m_nSigHist; j++){   int k;   doubletotalDiff;     )   k = (m_nFrameHist + nF − j) % m_nFrameHist;serve to loop the index k through the circular frame buffer, backwardsfrom position nF, as the index j runs from 0 to m_nSigHist−1.

The circular frame buffer holds up to a maximum of m_nFrameHist frames.However, as processing begins and the buffer accumulates successiveframes, the running length of the buffer is given by m_nSigHist. Thelines if(m_nSigHist < m_nFrameHist)   ++m_nSigHist; else   m_nSigHist =m_nFrameHist;increase the value of nSigHist as each new frame is added into thecircular buffer, up to the maximum size of m_nFrameHist.

After firstDif is determined, as described above, a second number,nDifs, is determined, in order to count the number of frames precedingthe candidate frame that differ from the current frame by more than thethreshold st. This is carried out at the lines // count the number offrames after our candidate that // differ from the current frame:if(diffHist[j] > st){   ++nDifs;

A third number, lastSame, is determined to indicate the oldest frame inthe circular buffer than is similar to the current frame, within athreshold SD_REJECT_THRESHOLD*st. This is carried out at the lines //reset the scan if we find a frame similar to the current one:if(diffHist[j] < SD_REJECT_THRESHOLD*st){   lastSame = j;

After the three parameters, firstDif, nDifs and lastSame have beendetermined, the logic for deciding whether or not the frame located atfirstDif is indeed a bona fide scene change is carried out at the linesif(firstDif >= m_nFrameHist/3 && nDifs > m_nFrameHist/3   && lastSame <=firstDif){   )

After AnalyseFrame( ) has found all of the scenes and determined thearray m_SceneList[ ], the method SceneList::jogScene(int nScenes, doublePosition) is used to run through the list of scenes. jogScene is calledwith a offset parameter, nScenes, and with a timecode position,Position. The array m_SceneList is searched for the first scene changetimecode that follows Position, this being the next scene to locate. Inorder not to provide the same scene change position as in an earliercall to jogScene, Position is first incremented by half of a frameduration.

It will be appreciated by persons skilled in the art that the presentinvention is not limited by what has been particularly shown anddescribed hereinabove. Rather the present invention includescombinations and sub-combinations of the various features describedhereinabove as well as modifications and extensions thereof which wouldoccur to a person skilled in the art and which do not fall within theprior art. APPENDIX A//================================================================= ==;// //  SceneDetector.h // // Scene Detector Filter // // Copyright (c)2000 MGI Software. All Rights Reserved. // // Author: Geoff Park ////--------------------------------------------------------------------------;#include “VideoIPTransform.h” #define MAX_SCENES 2000 #defineMAXFRAMEHISTORY 180 #define SCNDT_MODE_REVIEW 0 #defineSCNDT_MODE_ANALYSE 1 class SceneList { public:  // scene detectionparameters:  char m_SceneLogFileName[256];  FILE *m_SceneLogFile;  intm_grid;  int m_scale;  double m_threshold;  int m_nFrameHist;  intm_nSigHist;  int m_imgWidth;  int m_imgHeight;  doublem_frameAvgTimePerFrame;  // color histogram buckets  floatm_RBuckets[256];  float m_BBuckets[256];  float m_GBuckets[256];  floatm_oldRBuckets[MAXFRAMEHISTORY][256];  floatm_oldBBuckets[MAXFRAMEHISTORY][256];  floatm_oldGBuckets[MAXFRAMEHISTORY][256];  int m_nCurSceneNo, m_nSceneCount; double m_SceneList[MAX_SCENES];  //constructor  SceneList( ); //destructor  ˜SceneList( );  void init( );  void finit( );  boolAnalyseFrame(BYTE *pData, double time);  double jogScene(int nScenes,double Position); }; class CSceneDetector : public CVideoIPTransform,public IIPSceneDetectorFilt, public ISpecifyPropertyPages, publicCPersistStream { public:  DECLARE_IUNKNOWN;  static CUnknown * WINAPICreateInstance(LPUNKNOWN punk, HRESULT *phr);  // Reveals ISceneDetectorand ISpecifyPropertyPages  STDMETHODIMPNonDelegatingQueryInterface(REFIID riid, void ** ppv);  //CPersistStream stuff  HRESULT WriteToStream(IStream *pStream);  HRESULTReadFromStream(IStream *pStream);  // Overrriden from CVideoIPTransformbase class  HRESULT CheckInputType(const CMediaType *mtIn);  HRESULTCheckTransform(const CMediaType *mtIn, const CMediaType *mtOut); HRESULT GetMediaType(int iPosition, CMediaType *pMediaType);  HRESULTStopStreaming( );  HRESULT StartStreaming( );  // These implement thecustom IIPEffect interface  STDMETHODIMP put_GraphPosition(doublePosition);  STDMETHODIMP get_GraphPosition(double *Position, double*time, int *nScenes = NULL);  STDMETHODIMP jogScene(int nScenes); STDMETHODIMP jogFrame(int nFrames);  STDMETHODIMPput_AnalyseParams(double threshold,double window);  STDMETHODIMPget_AnalyseParams(double *pthreshold,double *pwindow);  STDMETHODIMPanalyse(void);  STDMETHODIMP get_SceneTime(int index, double *pTime); STDMETHODIMP init(void);  STDMETHODIMP finit(void);  STDMETHODIMPuseIMPos(bool usePos);  // ISpecifyPropertyPages interface  STDMETHODIMPGetPages(CAUUID *pPages);  // CPersistStream override  STDMETHODIMPGetClassID(CLSID *pClsid); private:  IMediaSeeking *m_pISeek; IMediaPosition *m_pIPos;  IMediaControl *m_pIControl;  // Constructor CSceneDetector(TCHAR *tszName, LPUNKNOWN punk, HRESULT *phr);  //Destructor  ˜CSceneDetector(void);  void NNResize(void *inPx, void*outPx);  // Look after doing the special effect  BOOLCanPerformSceneDetector(const CMediaType *pMediaType) const;  HRESULTTransform(IMediaSample *pMediaSample);  CCritSec m_FiltLock;   //Private critical section  int  m_effect;   // Which effect are weprocessing  bool m_needToCopyBuffer;  bool m_useIMediaPosition; unsigned int m_frameNum;  double m_frameAvgTimePerFrame; // in 100nsunits  double m_effectStartTime;  // When the text effect will begin double m_effectEndTime;  // When text effect ends  double*m_pPointTimes;  //  double *m_pPointValues;  //  double *m_pPointV2; //  int m_nPoints, m_maxPoints, m_curPoint;  const longm_lBufferRequest;  // The number of buffers to use  // filter mode:  intm_mode;  SceneList m_Scenes;  //HANDLE m_hWaitForASceneEvent; }; //SceneDetector//================================================================= ==;//  SceneDetector.CPP // //  Derived from EZRGB.CPP demo filter,Copyright (c) Microsoft Corporation. // //  Copyright (c) 1998 MGISoftware. All Rights Reserved. // //  $Revision: 1 $//--------------------------------------------------------------------------;// // // Summary // // This is a sample special effects filter - itworks only with RGB24 formats. // // // Demonstration instructions // //Start GRAPHEDT available in the ActiveMovie SDK tools. Drag and drop any// MPEG, AVI or MOV file into the tool and it will be rendered. Then goto // the video renderer box and disconnect its input pin from thefilter it is // connected to. Go to the Graph menu and select InsertFilters, from the // dialog select the Special Effects filter anddismiss the dialog. back in // the tool workspace connect the output ofthe decoder to the input of the // sample filter and then connect theoutput of the sample to the input of // the video renderer (GRAPHEDT mayput a colour space convertor in between) // // // Files // //SceneDetectorprop.cpp   A property page to control the video effects //SceneDetectorprop.h   Class definition for the property page object //SceneDetectorprop.rc   Dialog box template for the property page //SceneDetector.cpp   Main filter code that does the special effects //SceneDetector.def   What APIs we import and export from this DLL //SceneDetector.h   Class definition for the special effects filter //SceneDetector.reg   What goes in the registry to make us work //SceneDetectoruids.h   Header file containing the filter CLSIDs //iSceneDetector.h   Defines the special effects custom interface //makefile   How we build it... // resource.h   Microsoft Visual C++generated resource file // // // Base classes used // //CVideoIPTransform  MGI In-Place / Copy Video Filter Base Class. //CPersistStream  Handles the grunge of supporting IPersistStream. // //#include <stdio.h> #include <math.h> #include <windows.h> #include<streams.h> // Logfile location: #define SD_LOGFILE “\\TEMP\\Scene.Log”// Some Fudge Factors: #define SD_EDGE_FADEWIDTH 0.2 #defineSD_REJECT_THRESHOLD 1.2 #define SD_GRID_SUBSAMPLE 1 #defineSD_HIST_SUBSAMPLE 3 #define SD_LOW_THRESHOLD 2.0 #defineSD_HIGH_THRESHOLD 8.0 #define SD_DEFAULT_THRESHOLD 3.0 #defineSD_NFRAMES_IN_WINDOW 30 // constructor SceneList::SceneList( ){  m_grid= SD_GRID_SUBSAMPLE;  m_scale = SD_HIST_SUBSAMPLE;  m_threshold =SD_DEFAULT_THRESHOLD;  m_nFrameHist = SD_NFRAMES_IN_WINDOW;  m_nSigHist= 0;  strcpy(m_SceneLogFileName,SD_LOGFILE);  m_SceneLogFile = NULL; for(int i=0;i<256;i++){   m_RBuckets[i] = 0;   m_GBuckets[i] = 0;  m_BBuckets[i] = 0;  }  for(int nF=0;nF<MAXFRAMEHISTORY;nF++){  for(int i=0;i<256;i++){    m_oldRBuckets[nF][i] = 0;   m_oldGBuckets[nF][i] = 0;    m_oldBBuckets[nF][i] = 0;   }  } }//destructor SceneList::˜SceneList( ){ } void SceneList::init( ){ if(m_SceneLogFile != NULL)   fclose(m_SceneLogFile);  for(inti=0;i<MAX_SCENES;i++)   m_SceneList[i] = 0;  m_nSceneCount =m_nCurSceneNo = 0;  m_nSigHist = 0; } void SceneList::finit( ){ if(m_SceneLogFile != NULL)   fclose(m_SceneLogFile);  m_SceneLogFile =NULL;  m_nCurSceneNo = 0;  m_nSigHist = 0; } doubleSceneList::jogScene(int nScenes, double Position){  Position +=m_frameAvgTimePerFrame/2.0;  for(int i=0;i<m_nSceneCount;i++){  if(m_SceneList[i] > Position ) break;  }  i += nScenes − 1;  if(i < 0)i = 0;  if(i >= m_nSceneCount) i = m_nSceneCount − 1;  Position =m_SceneList[i];  m_nCurSceneNo = i;  return Position; }//--------------------------------------------------------------------------;// AnalyseFrame:  Detects scene changes. Called for each frame of video.// //  BYTE *pData  Pointer to image data in RGB format (3 bytes perpixel). //  double time Time in seconds since start of video. // //Method: // // Where: // // m_grid  - sample grid spacing, default=8 //nB   - number of color quantization levels, default=16 // m_nFrameHist - number of frames of history kept for analysis. // m_nSigHist  -frames considered significant, 0<m_nSigHist<=m_nFrameHist // // Pixelsare sampled from the image on a grid with spacing m_grid. // Each colorchannel is quantized into nB levels. For each color channel, // an arrayof nB buckets is used to record the number of pixels whose color //falls in each range. // // A circular history buffer of lengthm_uFrameHist is maintained for each // color channel. At any point intime m_nSigHist of these are considered // by the algorithm. When ascene is detected m_nSigHist is reset to the first // frame of the newscene. // // The differences of the current frame from each of them_nSigHist previous // frames are computed by summing the absolute valueof the differences of // each of the buckets in each color channel.These differences are recorded // in reverse chronological order in anarray, diffHist. // // A potential scene change is initially detected bylooking for successive // entries in this array whose difference exceedsa threshold. // // To reduce false triggering on lighting changes,camera flashes etc., some // additional conditions are required: // 1)The candidate frame must be preceded by m_nSigHist/3 similar frames, // so that we can be sure that a new scene exists. // 2) The framesfollowing the candidate frame must contain at least //  m_nSigHist/3frames that differ from the current frame. // 3) If a frame after thecandidate frame is encountered that differs from the //  current frameby less than half the threshold, the candidate frame //  is discardedand the search is reset. ////--------------------------------------------------------------------------;bool SceneList::AnalyseFrame(BYTE *pData, double time){  unsigned char*px;  int r,c,i,j;  // the number of bands in each histogram:  int nB =256>>m_scale;  // Frame count from the start of the effect:  intframeNum = (unsigned int) (time/m_frameAvgTimePerFrame);  // index intocircular buffer of historical frame statistics:  int nF = frameNum %m_nFrameHist;  for(i=0;i<nB;i++){   m_oldRBuckets[nF][i] =m_RBuckets[i];   m_oldGBuckets[nF][i] = m_GBuckets[i];  m_oldBBuckets[nF][i] = m_BBuckets[i];   m_RBuckets[i] = 0;  m_GBuckets[i] = 0;   m_BBuckets[i] = 0;  }  double wt, rwt;  double hb= m_imgHeight*SD_EDGE_FADEWIDTH;  double wb =m_imgWidth*SD_EDGE_FADEWIDTH;  for(r=0;r<m_imgHeight;r += m_grid){   px= pData + 3*r*m_imgHeight;   // weight pixels near edge less, to lesseneffect of camera jiggle:   rwt = 1.0;   if(r < hb) rwt = 1.0 − (hb −r)/hb;   if(r > m_imgHeight − hb) rwt = (m_imgHeight − r)/hb;  for(c=0;c<m_imgWidth;c += m_grid){    unsigned int red, green, blue;   wt = rwt;    // weight pixels near edge less, to lessen effect ofcamera jiggle:    if(c < wb) wt *= 1.0 − (wb − c)/wb;    if(c >m_imgWidth − wb) wt *= (m_imgWidth − c)/wb;    blue = px[0];    green =px[1];    red = px[2];    red >>= m_scale;    green >>= m_scale;   blue >>= m_scale;    m_RBuckets[red] += (float)wt;   m_GBuckets[green] += (float)wt;    m_BBuckets[blue] += (float)wt;   px += 3*m_grid;   }  }  // scale factor to compensate for image size,grid spacing, and frame rate:  double scale =255.0*(m_imgWidth/m_grid)*(m_imgHeight/m_grid)*m_frameAvgTimePerFrame; // scaled threshold:  double st = scale*m_threshold/100.0;  //difference of current frame with m_nSigHist previous frames:  doublediffHist[MAXFRAMEHISTORY];  if(m_nSigHist < m_nFrameHist)  ++m_nSigHist;  else   m_nSigHist = m_nFrameHist;  for(j=0;j <m_nSigHist; j++){   int k;   double totalDiff;   k = (m_nFrameHist + nF− j) % m_nFrameHist;   totalDiff = 0;   for(i=0;i<nB;i++){    totalDiff+= fabs(m_oldRBuckets[k][i] − m_RBuckets[i]);    totalDiff +=fabs(m_oldGBuckets[k][i] − m_GBuckets[i]);    totalDiff +=fabs(m_oldBBuckets[k][i] − m_BBuckets[i]);   }   diffHist[j] =totalDiff;  }  // scan the difference history for scene changes:  intnDifs, firstDif, lastSame;  nDifs = 0;  lastSame = 0;  firstDif = −1; nDifs = 0;  for(j=1;j<m_nSigHist;j++){   if(firstDif == −1){   lastSame = j;    if(diffHist[j] − diffHist[j−1] > st){     // Wefound a candidate:     firstDif = j;    }   } else {    // count thenumber of frames after our candidate that    // differ from the currentframe:    if(diffHist[j] > st){     ++nDifs;    }    // reset the scanif we find a frame similar to the current one:    if(diffHist[j] <SD_REJECT_THRESHOLD*st){     lastSame = j;    }   }  }  bool foundOne =false;  // It's really a scene change only if the new scene has at  //least m_nSigHist/3 similar frames, and the old one has  // at leastm_nSigHist/3 dissimilar ones.  // We also reject if frame similar tofirst frame appears later.  if(firstDif >= m_nFrameHist/3 && nDifs >m_nFrameHist/3   && lastSame <= firstDif){   double t;   t = time −firstDif*m_frameAvgTimePerFrame;   if(m_nCurSceneNo < MAX_SCENES){   m_SceneList[m_nCurSceneNo] = t;    ++m_nCurSceneNo;    m_nSceneCount= m_nCurSceneNo;    foundOne = true;   }   if(m_SceneLogFile != NULL){   fprintf(m_SceneLogFile,“%9.2f\n”,t);   }   // reset the historybuffer to the frame after the scene change:   m_nSigHist = firstDif;  } // always set a scene at first frame:  if(m_nCurSceneNo == 0){  m_SceneList[m_nCurSceneNo] = 0.0;   ++m_nCurSceneNo;   m_nSceneCount =m_nCurSceneNo;   foundOne = true;  }  return foundOne; } // EndAnalyseFrame */

1. A method for automatically detecting scene changes within a digitalvideo sequence including a succession of frames, comprising: identifyinga candidate frame that differs substantially from the predecessor frameto the candidate frame; determining whether a first plurality of frames,successively following the candidate frame, are substantially similar toone another; and further determining whether each of a second pluralityof frames, successively preceding the candidate frame, differsubstantially from a given frame, wherein the given frame follows thefirst plurality of frames.
 2. The method of claim 1 further comprisingmarking the candidate frame as a scene change frame, when saiddetermining determines that the first plurality of frames aresubstantially similar to one another, and when said further determiningdetermines that each of the second plurality of frames differssubstantially from a current frame.
 3. The method of claim 2 whereinsaid marking does not mark the candidate frame as a scene change frameif a frame preceding the candidate frame is substantially similar to thecurrent frame.
 4. A system for automatically detecting scene changeswithin a digital video sequence including a succession of frames,comprising: a frame identifier identifying a candidate frame thatdiffers substantially from the predecessor frame to the candidate frame;and a comparator determining whether a first plurality of frames,successively following the candidate frame, are substantially similar toone another, and determining whether each of a second plurality offrames, successively preceding the candidate frame, differssubstantially from a given frame, wherein the given frame follows thefirst plurality of frames.
 5. The system of claim 4 further comprising ascene change marker marking the candidate frame as a scene change frame,when said comparator determines that the first plurality of frames aresubstantially similar to one another, and that each of the secondplurality of frames differ substantially from the given frame.
 6. Thesystem of claim 5 wherein said scene change marker does not mark thecandidate frame as a scene change frame if a frame preceding thecandidate frame is substantially similar to the given frame.
 7. A methodfor automatically detecting scene changes within a digital videosequence including a succession of frames, comprising: identifying acandidate frame that differs substantially from the predecessor frame tothe candidate frame; determining whether a first plurality of frames,successively preceding the candidate frame, are substantially similar toone another; and further determining whether each of a second pluralityof frames, successively following the candidate frame, differssubstantially from an initial frame, wherein the initial frame precedesthe first plurality of frames.
 8. The method of claim 7 furthercomprising marking the candidate frame as a scene change frame, whensaid determining determines that the first plurality of frames aresubstantially similar to one another, and when said further determiningdetermines that each of the second plurality of frames differsubstantially from the initial frame.
 9. The method of claim 8 whereinsaid marking does not mark the candidate frame as a scene change frameif a frame following the candidate frame is substantially similar to theinitial frame.
 10. A system for automatically detecting scene changeswithin a digital video sequence including a succession of frames,comprising: a frame identifier identifying a candidate frame thatdiffers substantially from the predecessor frame to the candidate frame;and a comparator determining whether a first plurality of frames,successively preceding the candidate frame, are substantially similar toone another, and determining whether each of a second plurality offrames, successively following the candidate frame, differssubstantially from an initial frame, wherein the initial frame precedesthe first plurality of frames.
 11. The system of claim 10 furthercomprising a scene change marker marking the candidate frame as a scenechange frame, when said comparator determines that the first pluralityof frames are substantially similar to one another, and that each of thesecond plurality of frames differs substantially from the initial frame.12. The system of claim 11 wherein said scene change marker does notmark the candidate frame as a scene change frame if a frame precedingthe candidate frame is substantially similar to the initial frame.